Large diesel fuel engines for use in ships or power plants may use the technology of “pilot injection”. This technology may be used to lower engine noise. In such a case, the engine's electronic control unit can inject a small amount of diesel just before the main injection event, thus reducing its explosiveness in vibration, as well as optimizing injection time and quantity of variations in fuel quality, cold starting and so on. In some fuel systems like advanced common rail fuel systems as many as five or more injections per stroke may be used as “pilot injections”.
In order to insure that such large combustion engines in ships or power plants as well as in mechanical processing facilities operate for long periods of time without problems and interruptions, the fuels have to fulfil defined quality and cleanliness requirements, particularly the fuels used for the pilot injections. Fuels such as diesel fuel or marine diesel fuel are often contaminated with particles. Solid contamination is recognized as the main reason for the failure of injection nozzles and of early decay in fuel systems. Even if it is impossible to eliminate completely any contaminations, proper filter devices can be used to control most contaminations. The contamination level may be measured by counting the number of particles of a certain dimension per unit of volume of the fluid. This numbers then are classified in contamination classes, according to international standards, like ISO 4406:1999 or similar standards like SAE or NAS. Due to the fact that even diesel fuel or marine diesel fuel used in such large combustion engines for normal injections, as well as pilot injections, have a purity rate or cleanliness which is not acceptable for the injection equipment, the diesel fuel must be filtered.
In a worst case scenario the diesel fuel delivered fulfils only the contamination class ISO 25. For the injection equipment the contamination class ISO 11 may be acceptable only. That means the number of particles per 100 ml in the original fuel is more than 2.000.000, but the number of particles per 100 ml has to be reduced to 1.000 up to 2.000 at the maximum.
The necessary filtration of the diesel fuel may be conducted by a sequence of filters (“one pass filtration systems”). That sequence of filters might be cost-intensive and requires intensive maintenance work due to the often necessary filter exchanges. In addition, regular one pass filtration systems may need a lot of space. Further, it might be problematic to clean continuously the diesel fuel during operation of the engine. If a filter exchange is necessary normal operation of the internal combustion engine may not be possible.
Various devices for supplying and/or purifying fuel are known, for example, from JP 58 155263 A, JP 2009 241903 A, JP 11 200973 A, JP 58 059360 A, JP 62 051750 A, and EP 2 157 014 A.
U.S. Pat. No. 5,078,901 A shows a system for the automatic removal of contaminants such as water from the fuel supply of an internal combustion engine of the type including an auxiliary fuel tank. The system is automatically controlled and responsive to send contaminant levels in a contaminant removal mechanism and employs an existing fuel transfer pump to direct fuel around the auxiliary fuel tank through the contaminant removal mechanism. The pump additionally operates to provide a continuous supply of fuel to the engine to keep it operating while simultaneously permitting the discharge of contaminants from the contaminant removal mechanism when a predetermined maximum contaminant level has been reached. During normal operation fuel to be burned in the engine is drawn from the auxiliary fuel tank and the fuel decontamination mechanism. On its way to the engine from the auxiliary tank the fuel must pass through the fuel decontamination mechanism. In a start up mode fuel is caused to flow to bypass the auxiliary fuel tank. Accordingly, an exchange of a filter in the fuel decontamination mechanism is not possible during the normal operation.
Another system for cleaning contaminated fuel in a fuel tank is shown in U.S. Pat. No. 5,336,418 A. This known system for cleaning contaminated fuel in a fuel tank comprises a suction line introduced to substantially the lower most part of the tank for suctioning of free water and heavy contaminants settled in the tank. The materials are then rooted via suction through a first strainer, the free water and contaminants are trapped and retrieved. The filtrate then moves to a separation vessel, whereby the fuel is filtered through a primary filter medium, and the contaminants that settle to the bottom of the vessel are collected. The filtered fuel is then rooted to a tertiary filter before being returned to the fuel tank. The filtered fuel is discharged at the bottom of the tank with high velocity to stir up contaminants and facilitate their removal by the suction side of the system. This closed loop process is continued until the filtered fuel is substantially free of contaminants. Again, the closed loop filtering system does not provide the possibility to obtain continuously clean fuel when a filter exchange is necessary.
U.S. Pat. No. 7,681,556 B2 refers to a fuel supply system for use in heavy construction/force equipment including a primary fuel tank and a secondary fuel tank. The fuel supply lines of the two primary and secondary fuel tanks are connected in parallel to each other and are connected to a water separator.
U.S. Pat. No. 6,485,636 B1 shows a common usage of the diesel engines. The fuel filtration system allows the operator to keep the diesel engine running while inspecting a replacing one of the two fuel filters.
A fuel delivery system for multi-fuel engines is known from U.S. Pat. No. 7,546,835 B1. It provides the possibility to transfer at least some fuel from a first fuel storage region to a second fuel storage region via a pump during a first condition. At least some fuel is strained from the second fuel storage region to the first storage fuel region via gravity during a second condition. Fuel from the first fuel storage region is delivered to a first fuel injector of a cylinder of the internal combustion engine and fuel from the second fuel storage region is delivered to the second fuel injector of the cylinder. A similar system is known from U.S. Pat. No. 7,845,334 B2.
US 2010/0193415 A1 shows a fuel filtration device including a first filter normally used to filter foreign substances in fuel and a second filter used to filter foreign substances in fuel only in a state where a degree of blocking of the first filter is larger than the predetermined level. A regulating device is provided for regulating a flow of fuel through the second filter. The regulating device shall enable the flow of fuel through a second filter to permit the filtering of foreign substances through the second filter when the degree of blocking of the first filter is larger than the predetermined level.
Another dual fuel filtration system is known from U.S. Pat. No. 4,427,545 A.
U.S. Pat. No. 5,336,396 A shows a fuel management system for blending of an alternative fuel such as waste oil with a conventional fuel and for continuously filtering that fuel blend before delivery to the fuel injection system of a conventional diesel engine.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.